Readily assembled resolver having multiple pole pairs



. March 1969 H. c. BUNTSCHUH ET L 3,431,525

READILY ASSEMBLED RESOLVER HAVING MULTIPLE POLE PAIRS Original Filed May4, 1962 Sheet I Off.

I N V EN TOR. HENRY c. BUNTSCHUH /64 A puvo/s/N 'March 4,1969 UN S HUHETAL 3,431,525

33mm! ASSEMBLED RESOLVER HAVING MULTIPLE POLE PAIRS Original Filed May4, 1962 Sheet 3 of INVENTORS HENRY GEl/NTSCHUH JEHN A. auvolslN BY MXMATTQRNE Y5 United States Patent 3,431,525 READILY ASSEMBLED RESOLVERHAVING MULTIPLE POLE PAIRS Henry C. Buntschuh, New Hyde Park, N.Y., andJean A. Duvoisin, Westport, Conn., assignors to United AircraftCorporation, East Hartford, Conn., a corporation of Delaware Originalapplication May 4, 1962, Ser. No. 192,509, new Patent No. 3,332,144,dated July 25, 1967. Divided and this application Nov. 21, 1966, Ser.No. 606,490

US. Cl. 336-123 4 Claims Int. Cl. H01f 21/04 ABSTRACT OF THE DISCLOSUREAn air gap device in which the members carrying inductively cooperatingplanar conductive patterns are integral with or are connected directlyto race forming members between which rolling elements are disposed toprovide a compact assembly. The members all are formed of the samematerial.

This application is a division of our copending application Ser. No.192,509, filed May 4, 1962, now Patent No. 3,332,144.

There are known in the prior art resolvers having multiple pole pairsfor producing an electrical signal indicating the relative rotarydisplacement of one member with relation to another. One form of thisdevice includes conductive patterns deposited on glass plates which aremounted for relative rotation. The patterns are connected and energizedto produce an output signal representing the relative rotarydisplacement between the two plates. These devices are manufactured andsold under the trademark Inductosyn which is the registered trademark ofthe Inductosyn Corporation for position data producing devices of thetype described hereinabove. These devices, which will be identified bythe term Inductosyn hereinafter throughout the specification are shownand described in US. Patent No. 2,614,171, issued Oct. 14, 1952 to L. Fein for Electrical Apparatus for Measuring Angles.

The Inductosyn is a high precision device which derives its accuracyfrom the precision and stability of the engraved circuit patternscarried by glass plates. In order to permit the Inductosyns to functionwith the high degree of accuracy of which they are capable, it isessential that the rotor and stator plates be installed with a highdegree of concentricity. In the prior art special mounting flanges andadjustable centering means have been employed to permit the plates to becentered at the location at which they are installed. Even where theInductosyn is supplied as a package some mechanical coupling must beprovided between the package and the unit with which it is used, thusintroducing additional errors not compensated for by the adjustablemounting means for the rotor and stator plates.

While the auxiliary centering means described above can successfullyachieve the accurate centering required on installation the operation isa tedious and time-consuming one requiring a skilled technician for itsperformance. Not only is this true but also once the centering deviceshave been adjusted to cause the electrical centers of the devices tocoincide with the mechanical axis of rotation they are no longer usefuland become undesirable excess baggage. That is, once they have performedtheir function the centering means only add unwanted weight and occupyexcessive space. As is well known in the art of airborne instruments,considerations of weight and space are of prime importance.

Owing to the unequal coeflicient of expansion of the glass plates andthe bearing rings or flanges carrying the plates in the prior art,changes in temperature may introduce undesirable errors.

We have invented an Inductosyn which does not require any auxiliarycentering means at the location at which the device is installed. Ourdevice has an electrical center which coincides with the mechanical axisof relative rota tion of the device. The patterns of our Inductosyn maybe mounted directly on parts of rotary structures to form integral partsthereof. The mounting members can be of the same material as thebearings so that changes in temperature do not appreciably affect theaccuracy of our device. We have provided a method of making our improvedInductosyn.

One object of our invention is to provide an improved multiple pole pairresolver construction which overcomes the defects of similar devices ofthe prior art.

Another object of our invention is to vprovide an improved rotatingelectrical device which does not require auxiliary centering means forinsuring that the electrical center coincides with the mechanical centerof rotation.

A further object of our invention is to provide an Inductosyn which doesnot require the use of auxiliary centering means at the location atwhich it is installed.

Still another object of our invention is to provide an improvedInductosyn, the output of which is not seriously affected by changes intemperature.

A still further object of our invention is to provide a method forinsuring that the electrical centers of Inductosyn rotor and statorpatterns coincide with the axis of relative rotation of the memberscarrying the patterns.

Other and further objects of our invention will appear from thefollowing description:

In general our invention contemplates the provision of an improvedInductosyn in which the electrical centers of the rotor and statorpatterns are made to coincide with the mechanical center or axis ofrelative rotation of the members carrying the patterns in the course ofmanufacture of the rotor and stator. In one method of making our devicewe provide the bearing with a flange and mechanically scribe the flangewith a reference circle. We then make a template of the pattern to beplaced on the flange and provide the template with reference marks. Weproject the pattern and reference marks on the flange while coveringphoto-sensitive material under the pattern. We next adjust the positionof the flange until the reference circle and reference marks are alignedto indicate that the pattern image is concentric with the bearing race.When this is done, the pattern is photo-etched onto the flange.

In another method of making our Inductosyn we apply the pattern to therotor or stator, determine the electrical center of the pattern, andthen machine the element to insure that its mechanical center coincideswith the electrical center. In each of our methods, we may apply thepattern to a member made of the same material as the bearing so thatchanges in temperature will not adversely affect the operation of thedevice.

In the accompanying drawings which form part of the instantspecification and which are to be read in conjunction therewith and inwhich like reference numerals are used to indicate like parts in thevarious views:

FIGURE 1 is a sectional view of our improved Inductosyn.

FIGURE 2 is a plan view of the template we employ in one form of ourmethod of making our improved Inductosyn.

FIGURE 3 is a fragmentary view drawn on an enlarged scale of the paternwhich is to be applied to one of the Inductosyn members.

FIGURE 4 is a sectional view of an alternate form of our improvedInductosyn.

FIGURE 5 is a schematic view illustrating an alternate method of makingour improved Inductosyn.

Referring now to FIGURE 1 of the drawings, one form of our Inductosynindicated generally by the reference character is adapted to produce anoutput signal indicating the relative rotary displacement of members 12and 14. The Inductosyn 10 comprises a bearing having on outer ring 16provided with a race 18 and with a flange 20 for the reception of one ofthe Inductosyn rotor or stator patterns in a manner to be describedhereinabove. The bearing of the Inductosyn 10 includes a split innerring made up of an inner ring half 22 and an inner ring half 24. Thehalves 22 and 24 have grooves or races 26 and 28 which make up the innerrace of the bearing. We form the inner ring half 24 with a flange 30adapted to carry the other of the rotor and stator patterns of theInductosyn. These patterns maybe applied, for example, on insulatingmaterial 32 and 34 on the respective flanges 20 and 30.

Referring now to FIGURES l to 3, in one method of making our improvedInductosyn, in the course of manufacture of the raceway 18, for example,we scribe a reference circle 36, concentric with the raceway 18, on theflange 20 inside the area which is to receive the Inductosyn pattern.Similarly, in making the inner ring race 28 we scribe a reference circle40, concentric with the raceway 28, on the side of the flange 30 whichfaces flange 20 in the assembled bearing.

As can best be seen by reference to FIGURE 3 one of the Inductosynpatterns which is to be applied to a flange 20 or 30 includes aplurality of radially extending conductors 42 connected in series byconductive material 44. In this method of making our improved Inductosynwe apply the pattern including conductors 42 and material 44 by aphoto-etching process. In accomplishing this result we first make atemplate 48 of opaque material, illustrated in FIGURE 2, into which wecut a pattern 46 corresponding to the pattern of conductors 42 andconductive material 44 which is to be applied to the flange 20 or 30.This pattern 46 is, in effect, the negative of the patern which is to beapplied to the flange 20 or 30. In making the pattern 46 in the template48, we use a ruling engine with a circular dividing head. Since thedividing head indexes with the same degree of accuracy no matter whatdiameter template is employed, selection of a large diameter would notbe thought to contribute accuracy of the pattern produced. However,owing to the fact that the reciprocating motion of the head may not beas accurate as desired, we select a template 48 having a relativelylarge diameter. For example, if we assume that the cutter retraceswithin 10 microinches on a pattern having a mean radius of about 1 inch,the resulting angular error is about two seconds of arc. If a masterplate having a diameter of five times the actual pattern diameter isused, the error of the resulting pattern is only a fraction of a second.For a reason which will be explained hereinafter, we provide thetemplate 48 with four pairs of bracket type reference marks, each ofwhich includes an outer mark 50 and an inner mark 52.

Having prepared the template 48 in the manner described above we nextprepare the flanges 20 and 30 for the reception of the pattern. In thecourse of this operation we first place the insulating material 32. and34 on the facing sides of the flanges. Next the insulating material iscovered with conductive material as by plating. Assuming that theinsulating films 32 and 34 will not impair a high vacuum by out-gassing,evaporation techniques may be used instead of a wet plating process.Alternatively to plating, we may cement a thin foil to the flangepermitting the cement to act as the insulating material. After theconductive material has been applied to the flange, then it is coatedwith a photo-sensitive material which in turn is covered to prevent itsexposure before the pattern has been centered in a manner more fullydescribed in our copending application referred to hereinabove.

It is to be understood that while we have described a particularphoto-etching technique for applying the pattern to the rotor flange 30we could as well employ any other appropriate process. After we havecompleted the rotor we apply the proper pattern to the stator flange 20in a similar manner. When both the parts have had their patterns appliedthereto the rotor flange 30 is assembled on the shaft 74 of the member12 and the balls 76 are placed on shaft 24 and a nut 78 is turned on thethreaded end of the shaft to a distance which properly loads the bearingand gaps the rotor 30 and stator 20. Members 12 and 14 may be securedrespectively to the rotor 30 with stator 20 in any suitable manner knownto the art.

Referring now to FIGURE 4 we have shown an alternate form of ourInductosyn indicated generally by the reference character 80 including astator housing or flange 82 having a hub 84 which carries bearings 86and 88 for supporting the rotor housing or flange 90 of the assembly.Spacers 92 are provided for properly loading bearings 86 and 88 and forgapping the stator 82 and rotor 90. A preloading nut 94 is adapted to beturned down on the outside of hub 84 to apply the proper loading to thebearings. We may provide the hub 84 with a bore shield 96 disposedwithin the hub. Respective areas 98 and 100 of insulating material carrythe stator and rotor conductive patterns.

In making the form of our Inductosyn 80 shown in FIGURE 4 we first applythe stator conductive pattern to the face of the flange 82 adjacent therotor 90. This can be accomplished by any suitable manner known to theart such, for example, as by photo-etching or the like. As is known inthe art and as will be apparent from the description given hereinabove,the pattern is radial and axiosymmetric in nature. Thus it will have adefinite electrical center. In this form of our invention the flange 82does not have any reference circle scribed thereon and while great careis taken it is likely that the electrical center of the pattern on themember 82. will not coincide precisely with the mechanical center of thebore of hub 84.

Referring now to FIGURE 5, after having applied the rotor pattern to thearea of insulating material 100 we mount the member 90, for example, onthe movable plate of a rectangular coordinate positioning device 102similar to the device 56 shown in Duvoisin Patent No. 3,074,177. Asuitable chuck 104 mounts the device 102 on the spindle 106 of thetailstock 108 of a lathe indicated generally by the reference character110. It will thus be seen that the rotor 90 is mounted for rotationaround an axis while being positionable in a plane which isperpendicular to the axis of rotation.

We mount a master stator 112 of known accuracy on the tailstock 114 ofthe lathe 110. We connect the output conductors 116 and 118 of stator112 to a suitable indicating device such as a meter 120. Havingaccomplished the operations described above we move the tailstock 114 tothe left as viewed in FIGURE 5 until it is in inductive relationshipwith the rotor 90 thus to form a completed Inductosyn. With theInductosyn properly energized, we move the rotor 90 and stator 112 totheir various relative positions while noting the readings of meter 120.In accordance as the meter reading varies from what its output shouldbe, we actuate the device 102 to position rotor 90 to produce thecorrect output reading. When this has been done in all relativepositions of the rotor and stator so that the proper output readings areproduced we have determined the electrical center of the conductivepattern of the rotor 90. If this electrical center does not coincidewith the mechanical center of the base of the flange 90, we machine thebore of the rotor 90 to cause its mechanical center to coincide with theelectrical center just determined. This may readily be accomplished bymeans of a spindle grinding wheel 121 driven by a motor 122 carried bythe cross slide 124 of the lathe. As is known in the art, slide 124 iscarried in ways 126 which, in turn, can be moved left and right asviewed in FIGURE 5 along the bed of the lathe. With the wheel 120 inposition within the bore of the rotor 90, as the spindle 106 turns oneside of the bore of the rotor 90 will be ground down until the center ofthe bore coincides with the center of the electrical pattern which hasbeen placed thereon.

It will be appreciated that in manufacturing a number of our Inductosynswe first make as many of the rotors 90 as are required for the completedassemblies. Having done this we take the same number of stators 82 anddetermine their electrical centers in a similar manner. When the centerof a stator has been determined we may either grind the outside of thehub 84 or we may grind the hub bore. Assuming that a rotor 90 and astator 82 have been formed in the manner described above With theirmechanical centers of rotation corresponding precisely to the electricalcenters of the patterns carried thereby we then assemble the rotor 90and the stator 82 in inductive relationship by bearings 86 and 88,employing spacers 92 to insure that the plates are properly gapped andpredetermined.

It will readily be appreciated that in each form of our invention theInductosyn pattern is mounted on a member which has the same thermalcoefficient of expansion as do the bearings. Thus the outputs of ourdevice are not seriously affected by change in temperature.

In making our Inductosyn by the method illustrated in FIGURES l to 3 wescribe a reference circle such as the circle 40 on the member 30 duringthe course of formation of the race 28 so that the circle 40 isprecisely concentric with the race. We next cut the template 48 to thepattern to be applied to the member 30 and from the template with thereference marks 50 and 52. Having done this we deposit metal on theinsulating film 34 and cover the metal with photosensitive material.Next we proceed to form the pattern as described in our copendingapplication.

In making our Inductosyn by the method illustrated in FIGURES 4 and 5 Weapply the pattern to the member such for example as the member 90 by anymeans known to the art. We then mount the member 90 in the centeringdevice 102 and rotate it with reference to a standard 112 and thenadjust its position until the member 90 is mounted for rotation aboutthe electrical center of the pattern. When this has been accomplished wegrind the bore of the member 90 to make the center of the bore coincidewith the electrical center of the pat tern carried by the member 90.

It will be appreciated that the method illustrated in FIGURES 4 and 5also compensates for errors which might otherwise be introduced byvariations in pattern thickness and the like. By this method, too, thepatterns can be applied directly to relatively rotatable members of theequipment the condition of which is to be sensed and these members canthen be machined so that the electrical centers of the patterns coincidewith the mechanical centers of the members. That is, the patterns can bemade as integral parts of various rotating structures such as gyrogimbals and the like.

While we have shown and described our invention in connection with aninductive device it will readily be understood that it is equallyapplicable to any electrical air-gap device such as a capacitive device.

It will be seen that we accomplished the objectives of our invention. Wehave provided an Inductosyn which does not require any auxiliarycentering means at the location at which it is installed. Our device hasan electrical center which coincides with the center of rotation of themember carrying the pattern. The member carrying the pattern may be madeof the same material as the bearing material so that the accuracy of ourInductosyn is not atfected by changes in temperature.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsub-combinations are of utility and may be employed without reference toother features and sub-combinations. This is contemplated by and iswithin the scope of our claims. It is further obvious that variouschanges may be made in details within the scope of our claims withoutdeparting from the spirit of our invention. It is, therefore, to beunderstood that our invention is not to be limited to the specificdetails shown and described.

Having thus described our invention, what We claim is:

1. A multiple pole pair resolver assembly including in combination abearing comprising an inner ring and an outer ring and rolling elementsdisposed between said rings for relative rotation thereof around anaxis, a first member carrying a first generally circularly disposedelectrically conductive pattern providing a multiplicity of poles, saidfirst pattern having an electrical center, said first member beirlgfixedly mounted on said outer ring with said first pattern electricalcenter on said axis, and a second member carrying a second generallycircularly disposed electrically conductive pattern providing amultiplicity of poles, said second electrically conductive patternhaving an electrical center, said second member being fixedly mounted onsaid inner ring with said second pattern electrical center on said axis.

2. An assembly as in claim 1 in which said first and second members areformed of the same material as said rings.

3. An assembly as in claim 1 in which said first and second memberscomprise radially extending flanges providing surfaces facing each otherand areas of insulating material for supporting said conductive patternson said facing surfaces.

4. An assembly as in claim 1 in which said first and second memberscomprise radially extending flanges integrally formed with therespective bearing rings, said flanges providing surfaces which faceeach other and areas of insulating material for supporting saidconductive patterns on said facing surfaces.

References Cited UNITED STATES PATENTS 2,629,859 2/1953 Taylor 336-135XR 2,844,802 7/1958 Tripp et al. 336123 2,921,280 l/1960 Litwin er alsac-123 XR 3,202,948 8/1965 Farrand 336- LEWIS H. MYERS, PrimaryExaminer.

THOMAS J. KOZMA, Assistant Examiner.

U.S. Cl. X.R. 3l090

